1. Field of the Invention
The present invention relates to a method for processing a workpiece in a tool machine and a behavior measurement device.
2. Description of the Related Art
In a tool machine, problems those a motor is heated up by rotating a main axis and feeding an axis for relatively adjusting a position of a tool machine with respect to a workpiece and a member for constituting a tool machine such as a main axis is thermally displaced correspond to an ambient temperature in a location of the tool machine. For example, a working depth processed by a tool machine with respect to a workpiece is varied. Such problems make a phenomenon that a relative position between the workpiece and a working tool is slightly slipped. The phenomenon makes a processing error with respect to the workpiece.
The processing error as described above is largely influenced by thermal displacement of a main axis caused by rotating particularly. In a conventional art, in order to maintain a processing accuracy, a rotation of an axis without loading so call as an idling operation is continued until a thermal displacement is converged. After a convergence of the thermal displacement, a workpiece is begun to be processed.
In an idling operation, that is, in a time period from a moment when an idling operation time is started to a moment when a thermal displacement of a main axis is converged is varied corresponding to environment conditions at a space where a tool machine is located and a processing command with respect to the tool machine, so that an expert operator has to judge the time period with his/her best knowledge. Alternatively, the idling operation time is previously determined regardless of a rotational speed of a main axis influenced by thermal displacement. Therefore, a workpiece might be begun to be processed before a moment when the thermal displacement of the main axis is converged. Even if the idling operation time of the tool machine might be longer than a necessary time period that the tool machine is required. These are a reason why a working efficiency of the tool machine is lowered.
Concerning with these problems, a patent document 1 as described below discloses a tool machine comprising a device for measuring a position of a tool wherein a tip point of a sword is periodically measured and an idling operation is intermitted in the condition that a measured displacement amount of the tip point of the sword of the tool machine is within a range of acceptable error.    Patent Document 1: Japanese Patent Unexamined Document 2004-261934.